An image sensor uses opto-electronic components, such as photodiodes, to detect incoming light and produce electronic signals in response. A primary component of the image sensor is its sensor pixel array, wherein each pixel includes a photodiode to convert photons to charge carriers, a floating node to temporarily store the charge carries, and a number of transistor gates (transfer gate, source follower, reset transistor, etc.) to convey the charge carriers out of the pixel to be further processed by a peripheral circuitry. An image sensor is often packaged with its supporting elements into an image sensor package, which is then incorporated into an imaging product such as a mobile phone camera, a consumer electronic camera, a surveillance video camera, an automotive driver assistance device, a medical imaging endoscope, etc.
For the conventional chip scale package (CSP) of an image sensor, the cover glass is supported by dams which comprise insulation materials and adhesion materials, and are located on the periphery regions of the image sensor chip. When the image sensor continues scaled down, especially for stacking chip image sensor, there is less and less periphery area for dams to land on. Such small periphery area will limit the dam width and consequently cause CSP reliability issue.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.